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Old 10-07-2012, 10:59 PM   #1
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Gallons per hour

I've finally run two tanks through Mahalo and have two sets of data, both nearly identical. Twin Cummins 6bt turbos. I cruise about 9.5 knots, but always have periods of going slower and faster. Both engines combined, the boat gets 5.7 gph. How does that compare?
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Old 10-07-2012, 11:23 PM   #2
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Sounds optimistic but not unbelievable. The Coot, however, isn't capable of such high speeds or fuel consumption.
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Old 10-08-2012, 07:17 AM   #3
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Quote:
Originally Posted by Baggiolini View Post
I've finally run two tanks through Mahalo and have two sets of data, both nearly identical. Twin Cummins 6bt turbos. I cruise about 9.5 knots, but always have periods of going slower and faster. Both engines combined, the boat gets 5.7 gph. How does that compare?
What's your boat's length?

In my charter business, fuel is the number one expense. It's bigger than the next four (dockage, insurance, maintainance and capitol improvements) combined. So, if I change something like prop pitch, I do several trips varying the speed by a knot to determine fuel burn. Do this, and you might be surprised at how much fuel burn varies with your speed.

Ted
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Old 10-08-2012, 07:53 AM   #4
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Quote:
Originally Posted by Baggiolini View Post
I've finally run two tanks through Mahalo and have two sets of data, both nearly identical. Twin Cummins 6bt turbos. I cruise about 9.5 knots, but always have periods of going slower and faster. Both engines combined, the boat gets 5.7 gph. How does that compare?
To me it sounds about right...even very good on fuel burn for that speed...but more impressive is the speed...you must be throwing a pretty good wake at that speed.

Slow down to 7 knots and I bet your fuel burn will be about 1/3-1/2 of what it is now.
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Old 10-08-2012, 08:00 AM   #5
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Twin Cummins 6BT 330's, with a planing hull and 24000 lbs: 1300 rpm 7.4 kts and 5 gph.
Just to compare.

Shut one down: 1300 rpm, 6.5 kts and 2.5 gph.
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Old 10-10-2012, 10:43 AM   #6
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Quote:
Originally Posted by Baggiolini View Post
I've finally run two tanks through Mahalo and have two sets of data, both nearly identical. Twin Cummins 6bt turbos. I cruise about 9.5 knots, but always have periods of going slower and faster. Both engines combined, the boat gets 5.7 gph. How does that compare?
Compare? I burn 1.8 GPH at 2K RPM. That's seven knots in slack current (seven knots through the water). Since I boat in an area with reversing tidal currents, at any given time I could be making five to nine knots over land.

If I were to increase my speed to try to match yours, my fuel consumption would skyrocket. I suspect you could do much better if you slowed down to closer to hull speed. And maintained a constant RPM rather than trying to maintain a constant speed.
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